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回答时间：2025-01-13 10:41
以下是which和as的比较，希望能用上。
透析which与as在定语从句中的运用2007-11-01 22:47定语从句是高中英语的主要语法项目之一，也是高考英语的常考知识点，尤其是as和which引导的定语从句，更是历年高考试题中的重点和热点。as和which在引导定语从句时既有相同点又存在着很大的区别。
一、相同点
1. as和which都能引导定语从句，并都可以在定语从句中做主语或宾语，代表前面整个句子。
例 1 He married her, as / which was natural. 他跟她结婚了，这是很自然的事。
例 2 He is honest, as we can see. 他很诚实， 这一点我们看得出来。(表示人们从日常主观常识, 经验对某一事情的看法、评价,用as为妥。)
2. 当非限定性定语从句置于句末时，as和which都可用来引导这个定语从句。
例 3 The number of senior high school students is increasing, as is mentioned above. （as引导非限定性定语从句，意思是“正如”。此时也可以换用which引导，但意思有别，意思是：“这一点上面提到了”。）
二、不同点
（一）语义上的区别
as作为关系代词仍多少保留 “理由”“比较” “方式” “等同”等意义，而which没有这些意义。因此，由as引导的定语从句通常在意义上不可与主句相悖，而且一般是肯定的，对主句意义起相辅作用，表示 “正如”等意义；而which引导从句则不受此限制。
例 4 Mother treats me just like a baby，which I can’t bear． 妈妈对我就像小孩，我真受不了。
例 5 She has married again，which was unexpected． 她又结婚了，这是大家没有预料到的。
上面两句中的which都不宜用as。
但当否定的定语从句作正面理解，对主句起相辅作用而不是与其相悖时，仍可用as。
例 6 He turned his eyes on Philip’s face，as he had not done for ten years．他转过身来看着菲利普的脸，他十年来没有这样看过他的脸了。
例 7 He really can’t lend you the money，as you might not realize． 他的确不能把那些钱借给你，这一点你可能意识不到。
（二）用法上的区别
1. which与as引导非限制性定语从句的区别：
（1）which只能放在主句后面，而as引导的从句位置相对比较灵活，可以放在前，也可以放在后，甚至还可以分割主句。另外，as 常常有“正如、正像”的含义。
例 8 As he realized, I was very useful to him.（在前）
例 9 Air, as we know, is a gas. （在中）
例 10 He was a foreigner, as I know from his accent. (在后)
例 11 He came late again, which made his boss angry.（在后）
例 12 As is known to all, China is a developing country. 众所周知，中国是发展中国家。
（2）在which引导的定语从句中，谓语动词若是am, is, are，则这些系动词不能省略，而as后面若是这种情况，则可以省略。
例 13 He is a teacher, as (is) clear from his manner. (is可以省略)
例 14 He said he had never seen her before, which was not true. （was 不可省略）
（3）当which引导的从句在意义上近乎并列关系时，可以用and this, and that代替，意思是“这件事”。
例 15 He changed his mind, which(and this, and that) made me very angry. 他改变了主意，这使我很生气。
而as主要起与上下文连接的作用，表达说话人的看法、观点，并指出主句内容的出处或根据等。
例 16 Einstein, as we know, is a famous scientist.爱因斯坦，众所周知，是一位伟大的科学家。
例 17 As is announced in today’s newspaper, we must improve our style of work. 今天的报纸上说，我们必须改进工作作风。
（4）做主语时，which既可以作系动词be的主语，也可以作实义动词的主语，而这时as 只可以做系动词be的主语。
例 18 He married her, which was natural. （可用as代替which）他和她结婚，这是很自然的事。
例 19 He won a /the Nobel Prize in chemistry, which made him illustrious. (不可用as代替which)他获得了诺贝尔化学奖，这使他名扬天下。
（5）当定语从句位于主句之后，纯粹表示主句所述的内容，不带有“如……那样”的意思时，往往用which, 而不用as。
例 20 They were invited to the state banquet, which(as) was a great honor to them. 他们被邀请参加国宴，这对他们来说是莫大的荣幸。
例 21 We had to sleep in our wet clothes, which was most uncomfortable. 我们不得不穿着湿衣服睡觉，这简直太不舒服了。
（6）当定语从句有“如同……那样”的含义时，用as比用which更常见，而这些从句几乎成为固定说法。
例 22 Things will turn out contrary to one’s wishes, as is often the case. 事与愿违，这是常有的事。
例 23 As was natural, this inordinate hope was followed by an excessive depression.这种过分希望之后，接着是极度的沮丧，是很自然的事。
例 24 The material is elastic, as is show in the figure. 这种材料有弹性，如图所示。
例 25 As we know. 众所周知。
例 26 As has been said above/ before. 正如前文所述 。
（7）当定语从句的关系代词指的是先行词本身时，只能用which。
例 27 These apple trees, which I planted tree years ago, have not borne any fruit.这些苹果树是我三年前种下的，没结出任何果实。
例 28 The Thames, which is now clean enough to swim in, was polluted for over a hundred years.泰晤士河，现在已经很干净，可以在里面游泳，它曾被污染了一百多年。
（8）带介词的典型的定语从句，必须用which，不能用as。
例 29 There is a great deal of oxygen around us, without which we could not live. 我们周围有许多氧气，没有它我们就无法生存。
例 30 The shed in our garden, in which we often played, has lasted for a long time. 我们经常玩耍的花园里的那个棚子，已经有很长时间了。
（9）as常与从句中的know，see， hear，expect等动词连用，也常用于as often happens，as is often the case（常有的事）等句子中；而which一般不用于以上情况。
例 31 As is well known，Shanghai is a big city．
（10）当后置的非限制性定语从句是否定结构时，只能用which引导。
例 32 The result of the experiment was very good, which we hadn’t expected.
2. 引导限制性定语从句时which与as的区别：
(1)先行词如果是表示物的名词或代词，在从句中又做介词的宾语时，只能用which。
例 33 This is the pan in which I boiled the milk. 这就是我煮牛奶的锅。
（2）前面有as时,引导定语从句的关系代词用as, 不用which。
例 34 There are as many dictionaries as are needed.所需要的字典都有了。
（3）前面有such时，引导的定语从句的关系代词用as, 不用which。
例 35 Such women as know Tom thought he was charming. 认识汤姆的女人都认为他很迷人。
例 36 I have never heard such stories as he tells. 他讲的那些故事我从没听过。
（4）前面有the same时，引导定语从句的关系代词用as而不用which。
例 37 We are facing the same problems as we did years ago.我们正面临着和多年以前同样的困难。
例 38 This is the same wallet as I lost. 这只钱包与我丢失的那只相同。
（5）单个词引导限制性定语从句时，一般不用as而用which和that。由于关系词在从句中作宾语，which和that都可以省略。
例 39 The project which/that a British businessman has invested in is under construction at present.
（6）“介词+关系代词”引导定语从句时，只能用which。
例 40 Recently I bought an ancient Chinese vase, the price of which was very reasonable.
注：此时的which不能用as来代替。另外还应注意：引导定语从句时，which不能单独作定语，此时不管先行词是人还是物，都只能用whose引导，但指物时，可以用of which替换。
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